I play it nearly every day, I do expert on any instrument except Pro Keys and some songs as a Vocalist. However, I only play Pro Mode on Keys and Drums, I have my real guitar for Pro Mode. 4 or 5 star nearly every song that I play.
I own loads of DLC, I have basically any DLC the game has that I want, and I have every single RB game except Beatles and the AC/DC Live Track Pack, including exports.

Yep, I'm an addict alright. I've invested loads of time and money so far, but I just can't stop playing, and it's really fun when I have friends coming over, so I'd consider it a pretty good investment in my opinion.